Re: [Swig-user] lua binding with swig "void func(int* i); " and "void func(int& i); " how to ?

[Mark G. <ma...@go...>]

> hello, i got trouble binding and using function like
> 
> void func(int* i); and void func(int& i);
> 
> Main problem is, for int func(int& i), there is a call
> to lua_isuserdata()
> for my param,
> so in lua script:
> 
> <
> 
> varA = 10
> 
> func(varA) -> fails because varA is not a user data but
> a number
> 
> >
> 
> and for the int func(int* i), there is a call to isptrtype,
> problem is, how
> do i get a int * in LUA.
> 
> <
> 
> varA=10
> 
> func(&varA) ??? not working
> 
> i do not even know, how, from a int / number lua variable,
> can i get its
> reference and its pointer adress
> 
> Thank you for any help !
> 
> Thomas
> 

Hello Thomas,

What you have here is the standard SWIG attitude (everything else is a pointer).
Given the functions:
void func(int* i);
void func(int& i);
SWIG considers that both of them want an integer pointer (which is quite close, since references are wrapped as pointers).

There are two issues to address: one if how to select which one to use, the second is to use it properly.

I will look at the second issue:
assuming that they are both output functions (ie the parameter i is meant to be returned)
what you do is :
#include <typemaps.i>

%apply int* OUTPUT {int *i}; // int *i is output

void func(int *i);

Then when you call it in Lua, you get this effect.

i=func() -- returns i

If its really an input or input and output, then change the typemap to INPUT or INOUT accordingly.

As for the issue of which function to use: if your typemaps make the function signature sufficiently different, then all is good. Otherwise you will need to rename them
%rename(func_p) void func(int* i);
%rename(func_ref) void func(int& i);

Hope that helps,
If you are still not sure, please let me know.

Regards,
Mark